1 files changed, 41 insertions, 0 deletions
diff --git a/internal/auth/jwt.go b/internal/auth/jwt.go
new file mode 100644
index 0000000..a7fb52a
--- /dev/null
+++ b/internal/auth/jwt.go
@@ -0,0 +1,41 @@
+package auth
+
+import (
+	"errors"
+	"time"
+
+	"github.com/golang-jwt/jwt/v5"
+)
+
+const SessionTTL = 7 * 24 * time.Hour
+
+type Claims struct {
+	jwt.RegisteredClaims
+	UserID       int64 `json:"uid"`
+	TokenVersion int   `json:"ver"`
+}
+
+func IssueToken(secret []byte, userID int64, tokenVersion int, now time.Time) (string, error) {
+	c := Claims{
+		RegisteredClaims: jwt.RegisteredClaims{
+			IssuedAt:  jwt.NewNumericDate(now),
+			ExpiresAt: jwt.NewNumericDate(now.Add(SessionTTL)),
+		},
+		UserID:       userID,
+		TokenVersion: tokenVersion,
+	}
+	return jwt.NewWithClaims(jwt.SigningMethodHS256, c).SignedString(secret)
+}
+
+func ParseToken(secret []byte, tok string) (*Claims, error) {
+	var c Claims
+	_, err := jwt.ParseWithClaims(tok, &c, func(t *jwt.Token) (any, error) { return secret, nil },
+		jwt.WithValidMethods([]string{"HS256"}), jwt.WithExpirationRequired())
+	if err != nil {
+		return nil, err
+	}
+	if c.UserID == 0 {
+		return nil, errors.New("missing uid")
+	}
+	return &c, nil
+}